1. Field of the Invention
The present invention relates generally to imaging apparatus for developing electrostatic latent images to visualize the same in such devices as copying machines, laser printers and the like, and more particularly to an imaging apparatus having a transfer belt as a transfer/conveyer means for conveying a transfer material such as transfer paper and transferring a toner image formed on an image carrier onto the transfer material, and to a method for cleaning the transfer/conveyer means.
2. Description of the Related Art
Some of the transcription apparatus utilizing electrophotography employ a system using a dielectric belt and an insulating drum constituting a transfer/conveyer means for conveying a transfer material such as transfer paper and transferring a toner image onto the transfer paper. A cleaning mechanism is then required in the following cases:
(1) When a toner image is transferred onto a transfer/conveyer means: PA1 (2) When fogging toner is transferred: PA1 (3) When paper dust sticks to the transfer/conveyer means: PA1 cleaning means for removing deposits from the transfer/conveyer means is provided, on the downstream side of the charge furnishing means, in the direction in which the transfer/conveyer means is moved; more specifically, the cleaning means including: PA1 a cleaning member such as a blade or a brush which makes contact with the transfer/conveyer means and is used for removing deposits, PA1 joining-disjoining means such as an electromagnetic plunger for joining the image carrier and the transfer/conveyer means together and disjoining the latter from the former, the image carrier charged opposite in magnetic polarity to the deposits sticking to the transfer/conveyer means, and deposit removing means such as a photosensitive drum cleaner for removing deposits sticking to the image carrier. PA1 removing the deposits furnished with the charges, using a cleaning member in contact with the transfer/conveyer means, PA1 transferring the deposits which remain unremoved by the cleaning member to the image carrier, and PA1 removing the deposits transferred to the image carrier, using deposit removing means.
In a case where transfer paper which is being conveyed stops because of jamming or mechanical trouble and-fails to reach a transcription unit, a toner image formed on a photosensitive drum may be transferred not onto the transfer paper but onto a transfer/conveyer means directly. This arises from the fact that when the apparatus detects jamming or mechanical trouble and makes a control unit issue a halt instruction, the toner image on the photosensitive drum is allowed to reach the transcription unit before current is actually stopped from being supplied to the photosensitive drum, a drive motor as the transfer/conveyer means, and a transcriber. PA2 In a case where transfer paper whose width is smaller than that of transfer/conveyer means is used, no latent image is formed in a region where the transfer paper is not fed (where the belt does not contact the paper). However, the toner may stick to the background portion (the fogging phenomenon) and the fogging toner in that non-paper running region is transferred to the transfer/conveyer means. PA2 In addition, there is produced a space between sheets of paper when cut transfer paper is used. As in the non-paper running case, the fogging toner is transferred to the transfer/conveyer means as it is generated in the paper-to-paper space. PA2 The friction between transfer paper and rollers or the like in the conveyer system causes surface fibers to rub against the roller, thus producing paper dust. If the paper dust continues to stick to the transfer/conveyer means and is heavily accumulated, the adhesion of the transfer paper to the transfer/conveyer means will lower, which will also cause drum wrapping (a phenomenon in which the paper is attracted to the photosensitive drum side and rolled in thereon).
When characters are printed on the (front, rear, left-or right-hand) edge portion of the transfer paper, moreover, the transfer paper may be conveyed to the transcription unit as it slips out of position in relation to paper running accuracy. In this case, such a toner image is left in an outside portion close to the outer edge of the transfer paper.
A method for removing the dust comprises the steps of facilitating the removal of foreign substances sticking to the transfer/conveyer means by pretreatment with a corona charger and subsequently removing toner, using a blade of urethane or the like or a conductive brush to which bias opposite in magnetic polarity to the toner has been applied.
As such a blade is used to remove foreign substances by pressing its leading edge portion, the leading edge will wear off if it is used for a long time; its cleaning performance is thus lowered. In the case of a conductive brush, its cleaning performance will also be lowered because bristles tend to fall down or foreign substances are accumulated in the clearances of the bristles as it is continuously used.
When the cleaning performance of the transfer/conveyer means lowers, it is impossible to clean out a toner image sticking to the transfer/conveyer means. Then the residual toner will adhere to the back of the transfer paper subsequently fed, thus soiling the back of the transfer paper and deteriorating printing quality. Moreover, the lowered adhesion of the transfer paper to the transfer/conveyer means causes trouble such as the aforementioned drum wrapping.